1. Field of the Invention
The present invention relates to a dental implant having a core member formed of a gingiva-compatible metal for mounting a dental superstructure in the shape of a tooth crown; a fastening element for dental bridges or the like, wherein the core member is connected with a tissue-compatible biostable polymer matrix which contains reabsorbable, bioreactive sintered calcium phosphate.
2. Discussion of the Prior Art
Heretofore known and primarily employed implants consist of an anchoring component of metal and are shaped in the form of a plate, needle, screw or the like, and are based on a purely mechanical interengagement with the bone so as to achieve an anchoring of the prosthesis on the bone. In the interim it has been recognized that a plurality of technological material requirements must be fulfilled concurrently in order to be able to attain a permanent stable implantation. The utilized materials must be biocompatible with the bone and the configuration of the implant and the mechanical properties of the materials must provide a physiologically correct load and force distribution since, otherwise, the bone will react through deterioration and finally through loosening of the implant.
The shape of the implant and the instrumentability for its implanting must allow for a simple implanting which is correlated with the current conditions. The implant must in all areas provide for a direct, permanent and bone-like connection with the jaw and cannot be encapsulated with regard to the bone by a connective tissue membrane.
For this purpose, more recently there have become known bioactive materials which effect a connective tissue-free growing together of the bone with the material surface of the anchoring component. Such materials, for example, deal with calcium phosphate of a predetermined composition in which there occurs a direct connective tissue-free growing together of the bone with the material (Koster, "Experimenteller Knochenersatz durch resorbierbare Calciumphosphatkeramik", Langenbecks Archiv fur Chirogie 341, 77-86 (1976)). These calcium phosphates are decomposable in a biological milieu, meaning they are absorbed by the cells which are active during bone formation and thus fulfill the set basic biochemical requirement, nevertheless they do not come into consideration as the exclusive material for a permanently implanted prosthesis due to the lack of a permanent anchoring between the material of the anchoring component and the bone.
In order to produce a permanent anchoring of implants subject to high loads, in which there is achieved a really permanent connection between the prosthesis and the tissue, it has become known to formulate the prosthesis anchoring as a coating on the prosthesis shank, and to so embed the ceramic calcium phosphate having a particulate form of predetermined particle diameter size in the plastic material that, during the reabsorption of the ceramic component there is produced a matrix of plastic material which is porous throughout, and on whose inner pore surfaces there will remain bioactive residues of the ceramic.
In accordance with another proposal for an implantable tooth root, this consists essentially of a biostable polymer matrix which is compatible with human cell tissue, in which there is embedded the reabsorbable bioreactive calcium phosphate in a finely dispersed form, which is encompassed by a thin porous layer of non-reabsorbable calcium phosphate, and into which there is inserted a core as a connecting member for the mounting of a dental superstructure. Extraordinarily good results have been achieved with implants of that type, however, they are relatively complex, particularly with respect to the production of the polymer matrix with embedded calcium phosphate particles of predetermined construction.